Let me preface this by saying that I have read all the posts on the defrost door TSB. I do not think that this is my problem at all. I have a 2004, 2500 quad cab 4X4 with 52000 miles on it. EVERYTHING has been working fine up until tonight. I started her up and let her warm up for a minute or two and proceeded to drive off. When it got up to normal running temperature, I turned the middle "cold/hot" **** to hot and the far right selector to defrost. The selector had been in the "vent/floor" combination postion. The vents and floor continued to blow out cold air. The heat never came on nor would the air stop coming out of the vents/floor. Basically it seems to be permanently stuck in the mode it was in when I shut the truck off earlier today. The only **** working is the fan. In the 45 minute trip I took, I tried every combination of hot or cold and every position on the selector ****. Nothing ever changed and I ended up freezing my a$$ off by the time I got home, not to mention I could not see out the window. Any ideas on this TOTAL HVAC failure. Thanks.

Dan

 

sounds like a blend door to me.

 

It is a blown fuse...same thing happened to mine...open the fuse box under the hood and look for the AC/Heating or Climate ctrl fuse or whatever it is called. I think it is towards the back.

 

Thanks for the feedback so far but I think it's an electrical problem. I left the "cold/hot" **** in the hot position and the selector **** in the defrost position and today while driving, it all of a sudden began blowing heat and defrosting. As I was about to be momemtarily happy, all of my stock, factory sterio speakers quit. My radio was still on but I now have no sound. Is this some dumb "loose ground strap" issue or do I have a poltergeist in my truck?? Like I stated earlier, with 52000 miles on this vehicle, I have NEVER had a single problem with anything.
Dan